The long-term objectives of this proposal are two-fold: (1) to obtain more precise information concerning the chemical features of the plant protease inhibitor molecules which are responsible for its specific interaction with proteolytic enzymes, and (2) to evaluate the nutritional significance of these inhibitors. The interaction of the soybean trypsin inhibitor and trypsin will be studied with the specific aim of elucidating the structural features of the zone of contact between these two interacting species. This study will be extended to the double-headed soybean and lima bean inhibitors which are known to possess independent binding sites for chymotrypsin as well as trypsin. The nutritional studies will be directed to evaluating the nutritional significance of the trypsin inhibitor fraction of legumes. A study will also be made of the possible relationship between the distribution of genetic variants of the soybean trypsin inhibitor and the nutritional value of the soybean protein. The effect of removing the protease inhibitor and other growth-depressing factors from extracts of raw legumes by affinity chromatography will be studied in order to evaluate the role of these inhibitors as opposed to the effect of heat on the protein per se.